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PubMed2003

Micronized powders of a poorly water soluble drug produced by a spray-freezing into liquid-emulsion process.

The purpose of this paper is to investigate the influence of the emulsion composition of the feed liquid on physicochemical characteristics of drug-loaded powders produced by spray-freezing into liquid (SFL) micronization, and to compare the SFL emulsion process to the SFL solution process. Danazol was formulated with polyvinyl alcohol (MW 22,000), poloxamer 407, and polyvinylpyrrolidone K-15 in a 2:1:1:1 weight ratio (40% active pharmaceutical ingredient (API) potency based on dry weight). Emulsions were formulated in ratios up to 20:1:1:1 (87% API potency based on dry weight). Ethyl acetate/water or dichloromethane/water mixtures were used to produce o/w emulsions for SFL micronization, and a tetrahydrofuran/water mixture was used to formulate the feed solutions. Micronized SFL powders were characterized by X-ray diffraction, surface area, scanning and transmission electron microscopy, contact angle and dissolution. Emulsions containing danazol in the internal oil phase and processed by SFL produced micronized powders containing amorphous drug. The surface area increased as drug and excipient concentrations were increased. Surface areas ranged from 8.9 m(2)/g (SFL powder from solution) to 83.1 m(2)/g (SFL powder from emulsion). Danazol contained in micronized SFL powders from emulsion and solution was 100% dissolved in the dissolution media within 2 min, which was significantly faster than the dissolution of non-SFL processed controls investigated (<50% in 2 min). Micronized SFL powders produced from emulsion had similar dissolution enhancement compared to those produced from solution, but higher quantities could be SFL processed from emulsions. Potencies of up to 87% yielded powders with rapid wetting and dissolution when utilizing feed emulsions instead of solutions. Large-scale SFL product batches were manufactured using lower solvent quantities and higher drug concentrations via emulsion formulations, thus demonstrating the usefulness of the SFL micronization technology in pharmaceutical development.

Danazol↗
PubMed1999

Studies on the effect of pilocarpine incorporation into a submicron emulsion on the stability of the drug and the vehicle.

In order to obtain a novel ocular formulation with a potential for prolonging pilocarpine activity, the drug (2.0%) was incorporated into a submicron emulsion containing soya-bean oil and lecithin as emulgator. The effect of drug incorporation into the emulsion on its physical stability and on the other hand, the potential of the vehicle to reduce drug degradation at pH higher than 5.0 was studied. The pH was adjusted to 6.5 or 5.0 and the physicochemical stability of the formulations was observed. The mean diameter of oily particles in the resulting emulsions measured by a laser diffractometer was 0.6-0.7 micron and this was larger than in a drug-free emulsion where a 0.33 micron value was measured. The formulations were physically stable for 6 months at 4 degrees C, but progressing chemical degradation of pilocarpine was noted at pH 6.5. At that pH nearly 8% of pilocarpine was degraded to isopilocarpine and pilocarpic acid, both in the emulsion and in the solution. Thus, it may be concluded that pilocarpine in submicron emulsion is not protected against degradation. The presence of pilocarpine changes the physical stability of the vehicle since the formulation was easily destabilized during autoclaving or at room temperature. In the presence of higher concentration of lecithin (2.4%) or co-emulgators (poloxamer 2.0% or Tween 80 0.5%) the mean droplet size in the emulsions was the same as in a drug-free system. However the emulsions containing poloxamer were not stable during storage. Viscosity of pilocarpine emulsions can be increased by addition of methylcellulose or sodium carmellose (1.0%), but an intensive creaming occurs in these systems. Pilocarpine base is less suitable for emulsion preparation than hydrochloride salt, and emulsions prepared at pH 5.0 show the most satisfying stability.

Chemistry, Pharmaceutical↗
PubMed1997

Ethiodized oil emulsions in hepatic microcirculation: in vivo microscopy in animal models.

RATIONALE AND OBJECTIVES: The authors' purpose was to define the stability and drug-carrying and drug-releasing capacity of ethiodized oil emulsions in the hepatic circulation. METHODS: Emulsions prepared in various ratios of a nonionic contrast material containing doxorubicin to ethiodized oil were injected into the hepatic arteries of normal and tumor-bearing livers in rats or mice. In vivo microscopy was used to observe the dynamic distribution of the emulsions in the hepatic circulation. RESULTS: A solution of less water mixed with more oil formed water-in-oil (w/o) phase emulsions, whereas oil with more water formed oil-in-water (o/w) emulsions. The oil in the emulsions carried the water in the blood circulation. The w/o emulsions exhibited significantly higher carriage capacity and longer release time for the drug solution than did the o/w emulsions (P < .01). CONCLUSION: The delivery of w/o emulsions is superior to that of o/w emulsions. Further studies about preparation methods and delivery capability of emulsions in the liver are warranted.

Animals↗
PubMed2003

Production and characterization of O/W emulsions containing cationic droplets stabilized by lecithin-chitosan membranes.

Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion was prepared by homogenizing 5 wt % corn oil with 95 wt % aqueous solution (1 wt % lecithin, 100 mM acetic acid, pH 3.0) using a high-pressure valve homogenizer. This emulsion was diluted with aqueous chitosan solutions to form secondary emulsions with varying compositions: 1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0-0.04 wt % chitosan (pH 3.0). The particle size distribution, particle charge, and creaming stability of the primary and secondary emulsions were measured. The electrical charge on the droplets increased from -49 to +54 mV as the chitosan concentration was increased from 0 to 0.04 wt %, which indicated that chitosan adsorbed to the droplet surfaces. The mean particle diameter of the emulsions increased dramatically and the emulsions became unstable to creaming when the chitosan concentration exceeded 0.008 wt %, which was attributed to charge neutralization and bridging flocculation effects. Sonication, blending, or homogenization could be used to disrupt flocs formed in secondary emulsions containing droplets with high positive charges, leading to the production of emulsions with relatively small particle diameters (approximately 1 microm). These emulsions had good stability to droplet aggregation at low pH (< or =5) and ionic strengths (<500 mM). The interfacial engineering technology utilized in this study could lead to the creation of food emulsions with improved stability to environmental stresses.

Chitin↗
PubMed2003

Production and characterization of oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin-pectin membranes.

Oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin (beta-Lg)-pectin membranes were produced using a two-stage process. A primary emulsion containing small droplets (d(32) approximately 0.3 microm) was prepared by homogenizing 10 wt % corn oil with 90 wt % aqueous solution (1 wt % beta-Lg, 5 mM imidazole/acetate buffer, pH 3.0) using a high-pressure valve homogenizer. The primary emulsion was then diluted with pectin solutions to produce secondary emulsions with a range of pectin concentrations (5 wt % corn oil, 0.45 wt % beta-Lg, 5 mM imidazole/acetate buffer, 0-0.22 wt % pectin, pH 3.0). The electrical charge on the droplets in the secondary emulsions decreased from +33 +/- 3 to -19 +/- 1 mV as the pectin concentration was increased from 0 to 0.22 wt %, which indicated that pectin adsorbed to the droplet surfaces. The mean particle diameter of the secondary emulsions was small (d(32) < 1 microm) at relatively low pectin concentrations (<0.04 wt %), but increased dramatically at higher pectin concentrations (e.g., d(32) approximately 13 microm at 0.1 wt % pectin), which was attributed to charge neutralization and bridging flocculation effects. Emulsions with relatively small mean particle diameters (d(32) approximately 1.2 microm at 0.1 wt % pectin) could be produced by disrupting flocs formed in secondary emulsions containing highly negatively charged droplets, for example, by sonication, blending, or homogenization. The particles in these emulsions probably consisted of small flocs containing a number of protein-coated droplets bound together by pectin molecules. These emulsions had good stability to further particle aggregation up to relatively high ionic strengths (< or =500 mM NaCl) and low pH (pH 3). The interfacial engineering technology used in this study could lead to the creation of food emulsions with improved physicochemical properties or stability.

Chemical Phenomena↗
PubMed2004

Role of continuous phase protein on the oxidative stability of fish oil-in-water emulsions.

Whey protein isolate (WPI), soy protein isolate (SPI), and sodium caseinate (CAS) can inhibit lipid oxidation when they produce a positive charge at the interface of emulsion droplets. However, when proteins are used to stabilize oil-in-water emulsions, only a fraction of them actually absorb to the emulsion droplets, with the rest remaining in the continuous phase. The impact of these continuous phase proteins on the oxidative stability of protein-stabilized emulsions is not well understood. WPI-stabilized menhaden oil-in-water emulsions were prepared by high-pressure homogenization. In some experiments WPI was removed from the continuous phase of the emulsions through repeated centrifugation and resuspension of the emulsion droplets (washed emulsion). Unwashed emulsions were more oxidatively stable than washed emulsions at pH 7.0, suggesting that continuous phase proteins were antioxidative. The oxidative stability of emulsions containing different kinds of protein in the continuous phase decreased in the order SPI > CAS > WPI, as determined by both hydroperoxide and headspace propanal formation. Iron-binding studies showed that the chelating ability of the proteins decreased in the order CAS > SPI > WPI. The free sulfhydryls of both WPI and SPI were involved in their antioxidant activity. This research shows that continuous phase proteins could be an effective means of protecting omega-3 fatty acids from oxidative deterioration.

Caseins↗
PubMed2005

Production and characterization of oil-in-water emulsions containing droplets stabilized by multilayer membranes consisting of beta-lactoglobulin, iota-carrageenan and gelatin.

The influence of environmental conditions (pH, NaCl, CaCl2, and temperature) on the properties and stability of oil-in-water (O/W) emulsions containing oil droplets surrounded by one-, two-, or three-layer interfacial membranes has been investigated. Three oil-in-water emulsions were prepared with the same droplet concentration and buffer (5 wt % corn oil, 5 mM phosphate buffer, pH 6) but with different biopolymers: (i) primary emulsion: 0.5 wt % beta-Lg; (ii) secondary emulsion: 0.5 wt % beta-Lg, 0.1 wt % iota-carrageenan; (iii) tertiary emulsion: 0.5 wt % beta-Lg, 0.1 wt % iota-carrageenan, 0-2 wt % gelatin. The secondary and tertiary emulsions were prepared by electrostatic deposition of the charged biopolymers onto the surfaces of the oil droplets so as to form two- and three-layer interfacial membranes, respectively. The stability of the emulsions to pH (3-8), sodium chloride (0-500 mM), calcium chloride (0-12 mM), and thermal processing (30-90 degrees C) was determined. We found that multilayer emulsions had better stability to droplet aggregation than single-layer emulsions under certain environmental conditions and that one or more of the biopolymer layers could be made to desorb from the droplet surfaces in response to specific environmental changes (e.g., high salt or high temperature). These results suggest that the interfacial engineering technology used in this study could lead to the creation of food emulsions with improved stability to environmental stresses or to emulsions with triggered release characteristics.

Calcium Chloride↗
PubMed1992

Oral delivery of a renin inhibitor compound using emulsion formulations.

The oral delivery of O-(N-morpholino-carbonyl-3-L-phenylaspartyl-L- leucinamide of (2S,3R,4S)-2-amino-1-cyclohexyl-3,4-dihydroxy-6-methylhetane (I), a new renin inhibitor, was studied in the in vivo rat model using emulsion formulations. The components of the emulsion formulations were chosen based on their proposed effects on membrane structure, membrane fluidity, and solute transport. The percent absolute bioavailability (%AB) of I was increased from 0.3% (water suspension) to 5.1% when long-chain unsaturated fatty acid (oleic acid, linoleic acid, etc.)- and mono- and diglyceride (monolein, dilaurin, etc.)-containing emulsion formulations were used. Considering very high first-pass liver extraction of the compound (80%), it is suggested that emulsion formulations increased the intestinal transport of the compound significantly. The solubility of I in aqueous media with and without bile salt (20 mM) was found to be low (approximately 1 micrograms/ml). Incubation in 0.01 N HCl did not affect the particle size of the emulsion. The titration of oleic acid/monoolein emulsion in a pH 6.5 medium with a mixed bile salt system indicated reduction in the particle size of the emulsion. Drug precipitation was observed above 30 mM bile salt concentrations. No drug crystals could be detected in the intestinal contents of the rats when emulsion formulations were ingested. These results suggest that in the intestine of the animals, the particle size of the emulsions is reduced in the presence of bile fluid while the drug resides primarily in the oil phase. The mechanism of enhanced transport of I from the emulsion formulations is discussed along with the possibility of cotransport for the drug and oil. Emulsion formulations can be a potential delivery form for low-bioavailable lipid-soluble drugs.

Absorption↗
PubMed1995

Long-circulating emulsions (oil-in-water) as carriers for lipophilic drugs.

PURPOSE: Rapid clearance of parenterally administered oil-in-water emulsions from blood by the reticuloendothelial system (RES), mainly macrophages of the liver and spleen, has been one of the major obstacles for delivering lipophilic drugs to cells other than those in the RES. The purpose of this study therefore is to overcome this problem and develop emulsions that will have prolonged blood circulation time. METHODS: A series of amphipathic polyethylene-glycol (PEG) derivatives have been included as co-emulsifier into emulsions composed of Castor oil and phosphatidylcholine. The effect of amphipathic PEG on reducing the RES uptake and prolonging the blood circulation of the emulsion particles has been tested in vivo using mice as an animal model. RESULTS: Inclusion of PEG derivatives such as Tween-80 or dioleoyl N-(monomethoxy-polyethyleneglycol succinyl)phosphotidylethanolamine (PEG-PE) into emulsions composed of Castor oil and phosphatidylcholine decreases the RES uptake and increases blood residence time of the emulsions. The activity of PEG derivatives in prolonging the circulation time of emulsions depends on the PEG chain length (PEG2000 > PEG5000 > PEG1000, Tween-80) and the PEG density on emulsion surface. CONCLUSIONS: Inclusion of amphipathic PEG as emulsifier into oil-in-water emulsions is a very effective method to prolong the blood half life of the emulsions. Emulsions with long circulating half life in blood should be very useful as a delivery vehicle for lipophilic drugs.

Animals↗
PubMed1994

Physicochemical characterization and acute toxicity evaluation of a positively-charged submicron emulsion vehicle.

Fine, homogeneous, positively-charged emulsions with a mean droplet size of 138 +/- 71 nm and a zeta potential value of 41.06 mV were prepared using a combination of emulsifiers comprising phospholipids, poloxamer 188, and stearylamine. The pH of these emulsions decreased with time. However, the extent of decrease was dependent on the storage temperature. The mean droplet size of the emulsions that had been prepared with 1% poloxamer began to increase slightly after six months' storage, particularly when stored at 23 and 37 degrees C. However, emulsions prepared with 2% poloxamer remained stable for at least 10 months at 4 degrees C, suggesting that the poloxamer 188 concentration is critical for prolonged emulsion stability. The results of the ocular tolerance study in rabbit eye indicate that hourly administration of a positively-charged emulsion vehicle was well tolerated without any toxic or inflammatory response to the ocular surface during the five days of the study. Scanning electron microscopy revealed a normal corneal surface, which was not different from that of the animals treated with physiological saline. No marked acute toxicity was observed when 0.6 mL of positively-charged emulsion was injected intravenously to BALB/c mice. Furthermore, no difference was noted between this group of animals and the group injected with the marketed Intralipid emulsion. These results were further confirmed in a rat study where there were no deaths following intravenous injection of 3.3 mL per rat of the positively-charged emulsion or Intralipid. Neither emulsion elicited any hepatotoxic or nephrotoxic effects. The overall results suggest that the novel positively-charged emulsion is suitable for parenteral use, and for ocular application.

Amines↗
PubMed2006

Multiple emulsions: an overview.

Multiple emulsions are complex polydispersed systems where both oil in water and water in oil emulsion exists simultaneously which are stabilized by lipophillic and hydrophilic surfactants respectively. The ratio of these surfactants is important in achieving stable multiple emulsions. Among water-in-oil-in-water (w/o/w) and oil-in-water-in-oil (o/w/o) type multiple emulsions, the former has wider areas of application and hence are studied in great detail. Formulation, preparation techniques and in vitro characterization methods for multiple emulsions are reviewed. Various factors affecting the stability of multiple emulsions and the stabilization approaches with specific reference to w/o/w type multiple emulsions are discussed in detail. Favorable drug release mechanisms and/or rate along with in vivo fate of multiple emulsions make them a versatile carrier. It finds wide range of applications in controlled or sustained drug delivery, targeted delivery, taste masking, bioavailability enhancement, enzyme immobilization, etc. Multiple emulsions have also been employed as intermediate step in the microencapsulation process and are the systems of increasing interest for the oral delivery of hydrophilic drugs, which are unstable in gastrointestinal tract like proteins and peptides. With the advancement in techniques for preparation, stabilization and rheological characterization of multiple emulsions, it will be able to provide a novel carrier system for drugs, cosmetics and pharmaceutical agents. In this review, emphasis is laid down on formulation, stabilization techniques and potential applications of multiple emulsion system.

Animals↗
PubMed1994

Phagocytosis of a fluorescently labeled perflubron emulsion by a human monocyte cell line.

We hypothesized that fluorocarbon-based lipid emulsions are phagocytosed by monocytes and that many of the in vivo side effects related to the infusion of these particulate emulsions are due to release of cytokines by these monocytes. To clarify whether these emulsions are actually phagocytosed we attempted to measure by flow cytometry the apparent uptake of a fluorescently labeled high-concentration (90%, w/v) perflubron (perfluorooctyl bromide [PFOB]) emulsion by a differentiated human monocyte cell line. A fluorescent chromophore (Zynaxis Cell Science) was used to label the egg yolk phospholipid in a perflubron emulsion. This phospholipid label was used to track the perflubron emulsion during overnight incubation with the human monocyte (THP-1) cell line which had been differentiated, by exposure to PMA, into macrophage-like cells. Our results indicate that after 24 hours of incubation with the labeled perflubron emulsion, 64.9% (+/- 11.0) of differentiated THP-1 cells had cell-associated emulsion (ingested and/or membrane bound) whereas 24.4 (+/- 6.8%) of the control cells had cell-associated emulsion. We speculate that this technique may be a useful method to track the intravascular persistence and extravascular distribution of such emulsions, and that the degree of uptake of the emulsion by macrophages in this assay may correlate with its in vivo half life.

Cell Line↗
PubMed2006

Invited review: spray-dried dairy and dairy-like emulsions--compositional considerations.

Milk constituents [caseins, whey proteins (WP), lactose, and anhydrous milk fat] are used widely in the manufacture of dehydrated dairy and dairy-like emulsions. When sodium caseinate- (NaCas) and WP-stabilized emulsions with an oil-to-protein ratio ranging from 0.25 to 5 are dehydrated, NaCas is a more effective encapsulant than WP because of its superior emulsifying properties and resistance to heat denaturation. Denaturation degree of WP during drying has been associated with increased powder surface fat and larger droplet size after reconstitution. Encapsulation of NaCas-stabilized emulsions improves in the presence of lactose; powder surface fat was reduced from 30 to <5% when lactose was added at a 1:1 ratio to NaCas in an emulsion containing 30% (wt/wt) oil. This has been related to the ability of lactose to form solid-like (or glassy) capsules during sudden dehydration. Encapsulation of WP-stabilized emulsions is not improved by addition of lactose, although there are conflicting reports in the literature. Storage stability of dehydrated dairy-like emulsions is strongly linked to lactose crystallization as release of encapsulated material occurs during storage at high relative humidities (e.g., 75%). The use of alternative carbohydrates as "matrix-forming" materials (such as maltodextrins or gum arabic) improves storage stability but compromises the emulsion droplet size after reconstitution. The composition of the powder surface has been recognized as a key parameter in dehydrated emulsion quality. It is the chemical composition of the powder surface that dictates the behavior of the bulk in terms of wettability, flowability, and stability. Analyses, using electron spectroscopy for chemical analysis of the surface of industrial milk powders and dehydrated emulsions that mimicked the composition of milk, showed that powder surface is covered mainly by fat, even when the fat content is very low (18 and 99% surface fat coverage for skim milk and whole milk powders, respectively). The functional properties of milk constituents during emulsion dehydration are far from being thoroughly understood; future research needs include a) the encapsulation properties of pure micellar casein; b) a deeper understanding of colloidal phenomena (such as changes in the oil-water and air-oil interfaces) that occur before, during, and after dehydration, which ultimately define emulsion stability after drying; and c) reconciliation of the current different views on powder surface composition.

Animals↗
PubMedDate not supplied

Short- and long-term stability assessment of a new injectable diazepam submicron emulsion.

An innovative diazepam injectable emulsion, recently characterized, was submitted to short- and long-term stability studies. The initial pH of the diazepam emulsion decreased progressively with time. However, this pH decrease can be controlled by adjusting the initial pH of the emulsion. At initial adjusted pH of 7.4 or 8.0, the pH decrease of the emulsions was markedly diminished as confirmed by pH follow-up over 10 months storage. All the emulsions prepared using less than 25% oily phase remained stable at the various storage temperatures over a 10 month period. However, emulsion stability was highly dependent on the non-ionic emulsifier concentration, while both low and high phospholipid concentrations reduced emulsion stability. Furthermore, the diazepam remained intact in the emulsion, as confirmed by HPLC when stored at 4 degrees and 25 degrees C over a 16-month storage period. The optimal emulsion formulation was stable to conventional steam sterilization cycles. Exposure of the emulsion to mechanical stress conditions did not affect the integrity of the emulsion, indicating that the dosage form developed remained practically stable.

Diazepam↗
PubMed1995

Features of cholesterol structure that regulate the clearance of chylomicron-like lipid emulsions.

Cholesterol is an absolute requirement for the clearance from plasma of the remnants of triglyceride-rich lipoproteins. Our laboratory previously established that cholesterol was essential for the hepatic uptake of remnant particles after intravenous injection of chylomicron-like lipid emulsions (1). The aim of the present study was to determine the structural features of the cholesterol molecule that regulate the metabolism of chylomicrons. Chylomicron-like lipid emulsions, which reflect the size and composition and mimic the physiology of lymph chylomicrons, were prepared with tracer amounts of labeled triolein ([14C]TO) and cholesteryl oleate ([3H]CO) to follow the hydrolysis of triglyceride and the uptake of chylomicron remnant particles by the liver. Sterols selected as cholesterol congeners with functional group variations were incorporated into the emulsions in place of cholesterol and injected intravenously in rats. Control emulsions contained either no cholesterol or approximately 1% (by weight) cholesterol. The effects of the different sterol structures on lipolysis and hepatic remnant uptake were compared with controls to determine the significance of various functional groups. Clearance of emulsion CO was impaired when cholesterol was absent or replaced by cholesteryl chloride, cholesteryl formate, or 3-keto-cholesterol. Clearance of emulsions containing epicholesterol, where the OH group at the 3-position is in the alpha configuration, was similar to control emulsions containing cholesterol. Congeners with an additional hydroxyl group, viz. 7 alpha-hydroxycholesterol, 7 beta-hydroxycholesterol, or 25-hydroxycholesterol, reduced CO clearance. Androstenol, which lacks the side chain at the C17-position, also retarded CO clearance from plasma. In contrast, emulsions incorporating congeners with side chain variations such as campesterol, beta-sitosterol, stigmasterol, or saturated congeners of cholesterol such as cholestanol, coprostanol and its epimer, epicoprostanol, all were cleared similarly to emulsions containing cholesterol. In conclusion, for physiological clearance of a chylomicron-like emulsion, the presence of a hydroxyl (-OH) group at the 3-position and an alkyl side chain at the C17-position of cholesterol are essential, while the structure of the side chain and the saturation of the ring structure are not critical. The mechanism of the specificity of sterols on the metabolism of protein-free emulsions is unclear, but does not relate to changes in microfluidity of the surface lipids, nor to the amount or isoform of associated apolipoproteins.

Animals↗
PubMed1989

New high O2 carrying perfluorochemical emulsions and/or carbogen: reactions of a human tumor xenograft to irradiation.

The effects of two new perfluorochemical emulsions based on F-66E and PFOB which carry, in combination with carbogen, more oxygen than Fluosol-DA 20% were investigated on a human tumor xenograft (HRT18). Tumor bearing mice were pretreated with 15 ml/kg of F-66E emulsion (50 w/v%) or PFOB (100 w/v%) emulsion in the presence of carbogen for 1 hr prior to and during irradiation. F-66E emulsion was non toxic in vitro. In vivo, the dose modifying factor was 1.8 for mice pretreated with carbogen and F-66E emulsion whereas it was 1.6 for carbogen-breathing mice. Results with PFOB emulsion were similar to those obtained with F-66E emulsion. The effect of F-66E emulsion was studied using a fractionated radiation treatment: 12 Gy were delivered in 6 fractions of 2 Gy with an interval of 8 hrs between fractions. A single dose of F-66E emulsion was injected before the first irradiation. Surviving fractions were 0.35 for air-breathing mice, 0.091 for carbogen-breathing mice and 0.099 for carbogen-breathing mice pretreated with F-66E emulsion. These results showed that carbogen alone or carbogen plus F-66E or PFOB emulsion were very efficient even with low doses of radiation.

Animals↗
PubMed2006

Effect of dispersion pH on the formation and stability of Pickering emulsions stabilized by layered double hydroxides particles.

Using positively charged plate-like layered double hydroxides (LDHs) particles as emulsifier, liquid paraffin-in-water emulsions stabilized solely by such particles are successfully prepared. The effects of the pH of LDHs aqueous dispersions on the formation and stability of the emulsions are investigated here. The properties of the LDHs dispersions at different pHs are described, including particle zeta potential, particle aggregation, particle contact angle, flow behavior of the dispersions and particle adsorption at a planar oil/water interface. The zeta potential decreases with increasing pH, leading to the aggregation of LDHs particles into large flocs. The structural strength of LDHs dispersions is enhanced by increasing pH and particle concentration. The three-phase contact angle of LDHs also increases with increasing pH, but the variation is very small. Visual observation and SEM images of the interfacial particle layers show that the adsorption behavior of LDHs particles at the planar oil/water interface is controlled by dispersion pH. We consider that the particle-particle (at the interface) and particle-interface electrostatic interactions are well controlled by adjusting the dispersion pH, leading to pH-tailored colloid adsorption. The formation of an adsorbed particle layer around the oil drops is crucial for the formation and stability of the emulsions. Emulsion stability improves with increasing pH and particle concentration because more particles are available to be adsorbed at the oil/water interface. The structural strength of LDHs dispersions and the gel-like structure of emulsions also influence the stability of the emulsions, but they are not necessary for the formation of emulsions. The emulsions cannot be demulsified by adjusting emulsion pH due to the irreversible adsorption of LDHs particles at the oil/water interface. TEM images of the emulsion drops show that a thick particle layer forms around the oil drops, confirming that Pickering emulsions are stabilized by the adsorbed particle layers. The thick adsorbed particle layer may be composed of a stable inner particle layer which is in direct contact with the oil phase and a relatively unstable outer particle layer surrounding the inner layer.

Journal Article↗
PubMed2001

Behaviour of formula emulsions containing hydrolysed whey protein and various lecithins.

Formula emulsion systems are used as enteral, sports and health products. In some formulas addition of hydrolysed protein is necessary to guarantee ease of digestion and hypoallergenicity. In the low fat emulsion model an increase in the content of lecithin (phospholipid mixture) was required, in consideration of the advice of the Food and Nutrition Board (USA) for choline supplementation. The individual and interactive effects of whey protein isolate (WPI) or hydrolysate (WPH) (3.7 and 4.9% w/w), unmodified deoiled or hydrolysed lecithin (0.48 or 0.7% w/w) and carbohydrate in the form of maltodextrin with dextrose equivalent (DE) 18.5 or glucose syrup with DE 34 (11% w/w) on the properties of formula emulsions with 4% v/w sunflower oil, were investigated using a full factorial design. The emulsions were characterised by particle size distribution, coalescence stability, creaming rate, and also surface protein and lecithin concentration. WPI-containing emulsions proved to be stable against coalescence and showed only little creaming after 1 and 7 days standing. There was a significant increase in the mean droplet size and a significant deterioration of coalescence and creaming stability when WPH instead of WPI was used as the protein source, due to the lower number of large peptides and lower surface activity of the WPH. Increasing the WPH concentration led to an increase in oil droplet size and further deterioration of the stability of the emulsions. The starch hydrolysate and lecithin also significantly influenced the emulsion properties. Their influence was less strong when the emulsion contained WPI. Under the conditions used WPH-based emulsions were more stable, in terms of creaming and coalescence, when a low level of protein was used in conjunction with hydrolysed lecithin and glucose syrup. Oil droplets in emulsions containing unmodified lecithin in either the continuous or disperse phase and WPH in the continuous phase were very sensitive to coalescence. The addition of starch hydrolysates (DE 18.5) induced intensive flocculation and phase separation in these emulsions.

Journal Article↗